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Rotational Spectra of Four of the Five Conformers of 1-Pentene



Gerald T. Fraser, L H. Xu, R D. Suenram, C Lugez


The rotational spectra of four of the five expected conformers of 1-pentene, together with their monosubstituted 13C isotopic forms, have been measured in a molecular beam using a pulsed-nozzle Fourier-transform microwave spectrometer. One of the conformers has Cs point-group symmetry while the other three conformers have C1 point-group symmetry. The measurements are compared to results from molecular modeling calculations using the MM3 molecular-mechanics force field of Allinger et al. and to ab initio electronic structure calculations (MP2/6-31G*, MP2/6-311G*, MP4/6-31G*, MP4/6-311G*). Both types of calculations suggest the existence of five distinct conformers of 1-pentene, 4 of C1 symmetry and 1 of Cs symmetry. Both the MM3 and ab initio rotational constants deviate from the measured values by {less then or equal to} 5 %. The relatively high barriers between the four conformers limit the conformational cooling in the expansion, allowing all four conformers to be observed at the
Journal of Chemical Physics
No. 14


alkene, conformation, intermolecular forces, internal rotation, microwave spectroscopy, pentene


Fraser, G. , Xu, L. , Suenram, R. and Lugez, C. (2000), Rotational Spectra of Four of the Five Conformers of 1-Pentene, Journal of Chemical Physics (Accessed June 18, 2024)


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Created April 1, 2000, Updated February 17, 2017